Cellular Network (system)
In a cellular system, the service area is divided into cells. A transmitter is designed to serve an individual cell. The system seeks to make efficient use of available channels by using low-power transmitters to allow frequency reuse at much smaller distances.
A small geographical area refers to a cell.
The cellular concept replaces large transmitters with smaller transmitters. Neighboring Base Stations (BS) are assigned different sets of channels. Capacity can be increased by additional partition.
Factors for determining cell size;
Components and terminologies used in cellular network
It is a basic geographic unit of a cellular system. These are hexagonal structures that formed shaped networks.
-Cell size varies depending upon the landscape.
-The cell is defined as a radius of the circle that covers a particular area.
-The cell size is 100m in cities and 35km in the countryside.
-Each cell has its antenna, having a collection of transmitters, receivers, and control units.
-Adjacent cells are assigned with different frequencies to avoid interference.
The covered area of a cellular network is divided into smaller areas called cells.
-Each cell has a Base Station (BS) that provides direct communication with the mobile phones.
-There may be several base stations that are linked to a Base Station Controller (BSC). It acts as a small center to route cells to the required BS and also decides which cell suits which BS.
Channel per BTS=Available bandwidth/ (no. of station X per channel capacity)
It is a database that records the current location of each mobile that belongs to the MSC (Mobile Switching Center).
It is a database that records the visiting location of each mobile.
Cellular Telephone Systems
Provide connection to PSTN (Public Switched Telephone Network) for any user location within the radio range of the system.
Characteristics
Basic Cellular System
The basic cellular system consists of three parts:
Cellular telephone systems provide wireless connection to PSTN (Public Switched Telephone Network) for any user location within the radio range of the system.
A cellular system accommodates a large number of users over a large geographical area within a limited frequency spectrum. A cellular radio system provides high-quality service by limiting the coverage of each base station transmitter to a small geographical area called a cell so that the same radio channel may be reused by other base stations located some distance away.
Mobile Switching Center (MSC) also called Mobile Telephone Switching Office (MTSO) since it is responsible for connecting all mobiles to the PSTN in a cellular system.
The Mobile Station (MS) contains a transceiver. The transceiver is a combination of transmitter and receiver.
The Base Station (BS) consists of several transmitters and receivers which simultaneously handle full-duplex communications and general has towers that support several transmitters and receiving antennas.
The communication between the base station and mobile is defined by a standard common air interface.
The channel used for voice communication from the base station to mobile is called forward channels.
The channel used for voice communication from mobile to the base station is called reverse channels.
Advantages of Cellular System
Smaller the size of the cell more the number of concurrent users.
Huge cells require a greater transmission power than small cells.
They are more robust against the failure of single components, as they are decentralized.
In small cells, there is limited interference only.
Disadvantages of Cellular System
The mobile station has to perform a handover when changing from one cell to another cell very frequently.
The frequency spectrum should be distributed properly to avoid interference.
The small cell requires complex infrastructure to connect all base stations.
